Field of the Invention
The present invention relates to a spread spectrum clock generation circuit, a clock transfer circuit, an integrated circuit, and an image reading apparatus.
Description of the Related Art
There is known a spread spectrum clock generation circuit which performs spread spectrum for a reference clock having a constant frequency to generate a spread spectrum clock whose frequency varies, in order to reduce EMI (electromagnetic interference). Japanese Patent Laid-Open No. 2007-150560 proposes an image forming apparatus in which the former half of image processing is performed by a former image processing block operating in accordance with a reference clock, and the latter half of the image processing is performed by a latter image processing block operating in accordance with a spread spectrum clock. Output data from the former image processing block is supplied to an external memory controller. The external memory controller stores the data in an external memory. Thereafter, the external memory controller reads out data from the external memory and supplies the data to the latter image processing block. In this manner, the external memory controller operates as a clock transfer circuit.